Floodplain Soils and Drainage

Soil Pit Floodplain 2

This week we investigated a floodplain in the Finnis River area that is currently used for high intensity pasture production. The area was under investigation as during periods of high river flow the flood plain becomes inundated with water and then once the river subsides the water is left for a prolonged period ponding on the soil surface.

Due to the lie of the land and numerous natural depressions there is a dysfunctional pattern of flow that traps the water and prevents it from draining laterally off the field. In the investigation it was evident that there was elevated sodium and magnesium in the sub soil, resulting in dispersion and sealing of the clay which prevented the movement of water down through the more porous sub surface profile.

The owner is currently looking into levelling and redistributing the soil to improve the water runoff drainage management. A works in progress as the land forming begins next month.

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